1. Field of the Invention
The present invention relates to a lighting apparatus, and particularly to an electrodeless lighting apparatus using microwave.
2. Description of the Background Art
Recently, a lighting apparatus having an electrodeless light bulb using microwave wave has been developed. Since the electrodeless light apparatus has a long lifetimes and excellent light-emitting efficiency, a use thereof is being gradually increased. Hereinafter, an electrodeless lighting system according to the conventional art will now be described with reference to FIG. 1.
FIG. 1 is a view illustrating a structure of an electrodeless lighting apparatus using microwave according to the conventional art.
As shown in FIG. 1, an electrodeless lighting apparatus using microwave includes a power unit 10 for supplying AC power; a high voltage transformer (HVT) 13 for converting the AC power into a DC power of high voltage, and outputting the converted DC power of high voltage; a magnetron 14 receiving the DC power of high voltage and generating microwave; a waveguide 16 for inducing the microwave generated from the magnetron 14; an electrodeless light bulb 15 for emitting light by the induced microwave; a resonator 17 for cutting off the microwave by covering the front of the electrodeless light bulb 15, and passing the light emitted from the electrodeless light bulb 15 therethrough; and a cooling unit for cooling heat generated from the magnetron 14 and the high voltage transformer (HVT) 13. Hereinafter, operations of the electrodeless lighting apparatus using microwave according to the conventional art will now be described.
First, the HVT 13 converts AC power outputted from the power unit 10 into AC power of high voltage, converts the converted AC power into DC power, and outputs the converted DC power of high voltage to the magnetron 14.
The magnetron 14 receives the DC power of high voltage and generates microwave. Herein, the microwave is induced to the electrodeless light bulb 15 through the waveguide.
The electrodeless light bulb 15 generates light by the induced microwave. Herein the light is frontwardly emitted by a reflector 18.
Hereinafter, a structure of a voltage doubler unit of the HVT 13 will now be described with reference to FIG. 2.
FIG. 2 is a view illustrating a structure of a voltage doubler unit of the HVT according to the conventional art.
As shown therein, a voltage doubler unit within the high voltage transformer (HVT) 13 includes a first circuit unit 21 for converting AC power of high voltage generated from the HVT 13 into DC power of high voltage for the half of one period; and a second circuit unit 22 for converting AC power of high voltage generated from the HVT 13 into DC power of high voltage for another half of one period.
The first circuit unit 21 includes one side of a first capacitor (C1) connected to an output terminal of one side of the HVT 13; a (−) terminal of a first diode (D1) connected to the other side of the first capacitor (C1); and a (+) terminal of a third diode (D3) connected to the other side of the first capacitor (C1).
The second circuit unit 22 includes one side of a second capacitor (C2) connected to an output terminal of the other side of the HVT 13; a (−) terminal of a second diode (D2) connected to the other side of the second capacity (C2); and a (+) terminal of a fourth diode (D4) connected to the other side of the second capacitor (C2). Herein, the (+) terminal of the first diode (D1) and the (+) terminal of the second diode (D2) are connected to each other. That is, the voltage doubler unit is formed in a mirror type based on the earth of the HVT 13, and consists of circuits which are operated for different periods.
For example, for the half of one period, the first circuit unit 21 is operated to rectify AC power (voltage/current) corresponding to the half of one period for the half of one period, the second circuit unit 22 is operated to rectify AC power corresponding another half of one period for another half of one period.
However, in the high voltage transformer 13 of the electrodeless lighting apparatus using microwave according to the conventional art, when AC voltage inputted from the power unit 10 is changed (for example, when an instantaneous voltage change occurs), current which is applied to a filament of the magnetron 14 through the high voltage transformer 13 and the voltage doubler unit is changed, thereby shortening lifetimes of the magnetron. For example, if inputted voltage is change, outputted high voltage and current applied to a filament (cathode of magnetron) of the magnetron 14 are changed, and thus the magnetron 14 is put in an unstable state, thereby shortening lifetimes of the magnetron 14.
Besides, a lighting apparatus using microwave according to different conventional arts is described in detail in U.S. Pat. No. 6,608,443 registered on Aug. 19, 2003, U.S. Pat. No. 6,633,130 registered on Oct. 14, 2002 and U.S. Pat. No. 6,351,087 registered on Feb. 26, 2002.